The present invention relates generally to hair cutting devices having a bladeset including a moving blade reciprocating relative to a stationary blade and a drive system for powering the bladeset, and more specifically to a lubrication system for hair clippers or trimmers used for cutting hair of humans or animals.
Conventional hair cutting devices using a rotary drive system, such as hair trimmers and clippers typically include a drive member powered by the output shaft of the motor. For the purposes of this application, the terms “hair cutting device”, “hair clipper” and “hair trimmer” are considered interchangeable. The drive system converts rotary motion generated by the motor into linear motion in the form of the reciprocating moving blade relative to the stationary blade.
In a hair clipper drive system disclosed in U.S. Pat. No. 7,346,990 incorporated by reference herein, a driving end of the drive member follows a linearly reciprocating path as it engages the moving blade of the bladeset. In a production version of the invention disclosed in the '990 patent, the drive member is secured to a transverse shaft, also referred to as a linear drive shaft, which reciprocates with the drive member relative to the clipper frame. In some applications, over time, there has been excessive friction between the shaft and sleeve bushings mounted in the clipper frame. As a result, operational conditions, including heat and friction, combine to cause wear and deterioration of the sleeve bushings through which the linear drive shaft slides. Such wear decreases operational efficiency of the clipper and often increases operational noise.
Insufficient lubrication limits the ability to overcome what is known as “stiction.” Stiction is an informal combination of the term “static friction,” perhaps also influenced by the verb “stick.” Two solid objects, such as the linear drive shaft and a sleeve bushing, pressing against each other (but not sliding) will require some threshold of force parallel to the surface of contact to overcome static cohesion. Stiction is that threshold (not a continuous force) encountered during each cycle of the linear drive shaft when it changes direction. For a brief moment, the drive is stationary, and a “running oil film” that the sleeve bushings rely on for their service life is diminished. To obtain an extended life expectancy for the sleeve bushings on the linear drive shaft, a lubricant film should be reestablished once the drive shaft begins to move again.
Thus, there is a need for a lubrication system for a hair cutting device which addresses the above-identified problems of conventional units.